Combustion control apparatus for a diesel engine

Abstract

To suppress deposition of fuel injected at an early timing on a wall surface for preventing the degradation in fuel efficiency and increase in the amount of harmful components in an exhaust gas, in a direct-injection diesel engine which controls the injector to cause a combustion configuration dominated by the compressive ignition of the premixture while the engine is in the premixed combustion region defined on a low load side. When fuel is injected at an early timing to form the premixture, at least one of the pulse width to be inputted into the injector and the fuel pressure is or are adjusted according to the change in the injection timing, and corrected according to the intake air temperature or the intake pressure. If an allowable pulse width is insufficient to inject fuel in the amount corresponding to a target torque, fuel is injected in a divided manner.

What is claimed is: 
     
       1. A combustion control apparatus for a diesel engine comprising:
 an injector disposed so as to extend into a combustion chamber of a cylinder of the engine, and 
 an injection control means for controlling the injector to inject fuel at least during one of the intake stroke and compression stroke, so as to attain a first combustion state where the ratio of a premixed combustion is larger than that of a diffusion combustion, while the engine is in a predetermined operational condition, wherein, 
 said injection control means adjusts at least one of a period during which the injector opens its valve and the injection pressure of the fuel injected by the injector, at least based on a fuel injection timing, while the engine is in the predetermined operational condition, and 
 said injection control means performs at least one of the controls of shortening the valve opening duration of the injector as the fuel injection timing is advanced, and lowering the injection pressure as the fuel injection timing is advanced. 
 
     
     
       2. A combustion control apparatus for a diesel engine as defined in  claim 1 , wherein,
 said injection control means controls the injector to inject fuel in a divided manner with a plurality of shots, when an amount of the fuel injection corresponding to a required torque exceeds a maximum fuel injection amount attainable within a valve opening duration of the injector. 
 
     
     
       3. A combustion control apparatus for a diesel engine as defined in  claim 2 , wherein
 said injection control means controls the injector so that the valve opening durations for the respective divided shots are prolonged for a more retarded crank angle. 
 
     
     
       4. A combustion control apparatus for a diesel engine as defined in  claim 1 , further comprising,
 an exhaust gas recirculation passage for recirculating a part of exhaust gas into an intake passage of the engine, 
 an exhaust gas recirculation amount regulator valve for adjusting the amount of the recirculated exhaust gas through the exhaust gas recirculation passage, and an exhaust gas recirculation control means for controlling the opening of the exhaust gas recirculation amount regulator valve. 
 
     
     
       5. A combustion control apparatus for a diesel engine as claimed in  claim 1 , wherein,
 said fuel injection control means controls the injector to inject fuel during the intake stroke or during the compression stroke, so as to cause the first combustion configuration while the engine is in a first region defined on the low load side, and to inject fuel at a timing near the top-dead-center of the compression stroke, so as to cause a second combustion configuration where the ratio of the diffusion combustion is larger than that of the premixed combustion while the engine is in a second region different than the first region. 
 
     
     
       6. A combustion control apparatus for a diesel engine as claimed in  claim 5 , wherein,
 said injector is provided with a hole-type nozzle. 
 
     
     
       7. A combustion control apparatus for a diesel engine as claimed in  claim 5  wherein,
 the engine is equipped with a charging device for charging intake air, and 
 said injection control means controls the injector to inject fuel in a divided manner with a plurality of divided shots while the engine is in a higher engine load side defined on the first predetermined operational condition region, and performs at least one of controls wherein the valve opening duration is more prolonged than that having the same number of divisions in the divided injection under the operational condition on the lower load side; and the injection pressure is larger than that having the same number of divisions in the divided injection under the operational condition on the lower load side. 
 
     
     
       8. A combustion control apparatus for a diesel engine comprising:
 an injector disposed so as to extend into a combustion chamber of a cylinder of the engine, and 
 an injection control means for controlling the injector to inject fuel at least during one of the intake stroke and compression stroke, so as to attain a first combustion state where the ratio of a premixed combustion is larger than that of a diffusion combustion, while the engine is in a predetermined operational condition, wherein, 
 there is provided an intake air temperature detecting means for detecting intake air temperature, 
 said injection control means adjusts at least one of a period during which the injector opens its valve and the injection pressure of the fuel injected by the injector, at least based on the intake air temperature detected by the intake air temperature detecting means, while the engine is in the predetermined operational condition, and 
 said injection control means performs at least one of the controls of shortening the valve opening duration of the injector for a higher temperature detected by the intake air temperature detecting means, and lowering injection pressure for the higher temperature detected by the intake air temperature detecting means. 
 
     
     
       9. A combustion control apparatus for a diesel engine as defined in  claim 8  wherein,
 said injection control means controls the injector to inject fuel in a divided manner with a plurality of shots, when an amount of the fuel injection corresponding to a required torque exceeds a maximum fuel injection amount attainable within a valve opening duration of the injector. 
 
     
     
       10. A combustion control apparatus for a diesel engine as defined in  claim 9  wherein
 said injection control means controls the injector so that the valve opening durations for the respective divided shots are prolonged for a more retarded crank angle. 
 
     
     
       11. A combustion control apparatus for a diesel engine as defined in  claim 8  further comprising,
 an exhaust gas recirculation passage for recirculating a part of exhaust gas into an intake passage of the engine, 
 an exhaust gas recirculation amount regulator valve for adjusting the amount of the recirculated exhaust gas through the exhaust gas recirculation passage, and an exhaust gas recirculation control means for controlling the opening of the exhaust gas recirculation amount regulator valve. 
 
     
     
       12. A combustion control apparatus for a diesel engine as claimed in  claim 8  wherein,
 said fuel injection control means controls the injector to inject fuel during the intake stroke or during the compression stroke, so as to cause the first combustion configuration while the engine is in a first region defined on the low load side, and to inject fuel at a timing near the top-dead-center of the compression stroke, so as to cause a second combustion configuration where the ratio of the diffusion combustion is larger than that of the premixed combustion while the engine is in a second region different than the first region. 
 
     
     
       13. A combustion control apparatus for a diesel engine as claimed in  claim 12  wherein,
 said injector is provided with a hole-type nozzle. 
 
     
     
       14. A combustion control apparatus for a diesel engine as claimed in  claim 12 , wherein,
 the engine is equipped with a charging device for charging intake air, and 
 said injection control means controls the injector to inject fuel in a divided manner with a plurality of divided shots while the engine is in a higher engine load side defined on the first predetermined operational condition region, and performs at least one of controls wherein the valve opening duration is more prolonged than that having the same number of divisions in the divided injection under the operational condition on the lower load side; and the injection pressure is larger than that having the same number of divisions in the divided injection under the operational condition on the lower load side. 
 
     
     
       15. A combustion control apparatus for a diesel engine comprising:
 an injector disposed so as to extend into a combustion chamber of a cylinder of the engine, and 
 an injection control means for controlling the injector to inject fuel at least during one of the intake stroke and compression stroke, so as to attain a first combustion state where the ratio of a premixed combustion is larger than that of a diffusion combustion, while the engine is in a predetermined operational condition, wherein, 
 there is provided an intake air pressure detecting means for detecting the pressure of intake air, 
 said injection control means adjusts at least one of a period during which the injector opens its valve and the injection pressure of the fuel injected by the injector, at least based on the intake air pressure detected by the intake air pressure detecting means, while the engine is in the predetermined operational condition, and 
 said fuel injection control means performs at least one of the controls of shortening the valve opening duration for a lower pressure detected by the intake air pressure detecting means, and lowering the injection pressure for the lower pressure detected by the intake air pressure detecting means. 
 
     
     
       16. A combustion control apparatus for a diesel engine as defined in  claim 15  wherein,
 said injection control means controls the injector to inject fuel in a divided manner with a plurality of shots, when an amount of the fuel injection corresponding to a required torque exceeds a maximum fuel injection amount attainable within a valve opening duration of the injector. 
 
     
     
       17. A combustion control apparatus for a diesel engine as defined in  claim 16 , wherein
 said injection control means controls the injector so that the valve opening durations for the respective divided shots are prolonged for a more retarded crank angle. 
 
     
     
       18. A combustion control apparatus for a diesel engine as defined in  claim 15 , further comprising,
 an exhaust gas recirculation passage for recirculating a part of exhaust gas into an intake passage of the engine, 
 an exhaust gas recirculation amount regulator valve for adjusting the amount of the recirculated exhaust gas through the exhaust gas recirculation passage, and an exhaust gas recirculation control means for controlling the opening of the exhaust gas recirculation amount regulator valve. 
 
     
     
       19. A combustion control apparatus for a diesel engine as claimed in  claim 15 , wherein,
 said fuel injection control means controls the injector to inject fuel during the intake stroke or during the compression stroke, so as to cause the first combustion configuration while the engine is in a first region defined on the low load side, and to inject fuel at a timing near the top-dead-center of the compression stroke, so as to cause a second combustion configuration where the ratio of the diffusion combustion is larger than that of the premixed combustion while the engine is in a second region different than the first region. 
 
     
     
       20. A combustion control apparatus for a diesel engine as claimed in  claim 19  wherein,
 said injector is provided with a hole-type nozzle. 
 
     
     
       21. A combustion control apparatus for a diesel engine as claimed in  claim 19  wherein,
 the engine is equipped with a charging device for charging intake air, and 
 said injection control means controls the injector to inject fuel in a divided manner with a plurality of divided shots while the engine is in a higher engine load side defined on the first predetermined operational condition region, and performs at least one of controls wherein the valve opening duration is more prolonged than that having the same number of divisions in the divided injection under the operational condition on the lower load side; and the injection pressure is larger than that having the same number of divisions in the divided injection under the operational condition on the lower load side.